// function that takes 10 digits and returns a string of the formatted phone number
// e.g.: 1234567890 -> (123) 456-7890

const formatPhoneNumber = ( numbers ) => {
  const numbersString = numbers.toString()
  if ( ( numbersString.length !== 10 ) || isNaN( numbersString ) ) {
    // return "Invalid phone number."
    throw new TypeError( 'Invalid phone number.' )
  }
  const arr = '(XXX) XXX-XXXX'.split( '' )
  Array.from( numbersString ).forEach( n => {
    arr[ arr.indexOf( 'X' ) ] = n
  } )
  return arr.join( '' )
}

export {
  formatPhoneNumber
}
